How to create stylize hair shader
You could try it with a curve that you bevel with a second curve as Bevel Object and a third as Taper Object. For the material it looks like a painted picture (a bit more stylized than what I've used here), so maybe use an image editor then import into an Image Texture node? Then duplicate, and probably convert to mesh to work the shape a bit more precisely (keep it low-poly like in your picture):




You could also try a procedural material:


From what you say, in your reference image, the hair are painted, it makes things much easier, so maybe mix painted and procedural effects (particularaly bumps and glossy effects):